The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore.
(1) Field of the Invention
The present invention relates generally to a transceiver for data communication, and more particularly to a Radio Frequency (RF) front end to a standard IF (Intermediate Frequency) modem to allow full duplex data communication at RF.
(2) Description of the Prior Art
For a full duplex communication transceiver, the transceiver""s transmitter and receiver are simultaneously active, thereby allowing simultaneous data transmission and reception. Depending upon the design considerations, a full duplex transceiver""s transmit and receive antennae are often the same. When transmit and receive frequencies are similar, interference is often encountered although separate transmission and receive antennae are employed.
Methodologies and systems for avoiding transmit and receive signal interference include U.S. Pat. No. 5,905,706 to Vidales wherein half-bit transmission and reception intervals are formed; U.S. Pat. No. 5,715,520 to Hillock, et al, for Time Division Duplex (TDD) systems to utilize a single Local Oscillator (LO) to derive two LO signals at different times, thereafter using the two LO signals to produce an intermediate and an offset signal frequency; U.S. Pat. No. 5,687,169 to Fullerton describes a pulse interleaving method and apparatus for impulse radio""s ultrawide-band communications; and, U.S. Pat. No. 5,533,056 to Cripps provides a duplex transceiver binary encoder/decoder.
U.S. Pat. No. 5,881,369 to Dean, et al, describes a duplex receiver operational in Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes. The Dean, et al, transceiver has an up-conversion path that converts an Intermediate Frequency (IF) to a Radio Frequency (RF) in either an upper RF frequency range or a lower RF frequency range, and similarly a down-conversion path to convert the received RF frequency in either the upper or lower frequency range to a desirable IF frequency. The Dean, et al, up-conversion and down-conversion paths connect to either an upper or lower band diplexer port through a switch array. A switch controller controls the switch array based upon whether the transceiver is operating in TDD or FDD mode. The Dean, et al, invention concentrates on cellular communication requirements and demands.
General data communication between a transmitter and receiver are less restrictive than the cellular requirements. Higher frequency data communication allows more rapid communication rates; however, typical modems for data communication operate in the IF frequency band.
There is currently no apparatus or method for a full duplex transceiver at the Radio Frequency (RF) bands, wherein RF is derived from a variable IF frequency.
What is needed is a method and apparatus to convert an IF generator output to RF for full duplex communication.
It is a general purpose and object of the present invention to provide a configurable transceiver architecture that allows simplex, half-duplex, and full duplex operation. Another object of the present invention is to provide a transceiver architecture that accepts a variable IF as input, and generates a RF output for data communication using fixed Phase Locked Oscillators (PLOs). A further object is to provide a transceiver that receives a RF signal and converts the RF signal to an IF signal using fixed PLOs. Still yet another object is to provide such configurable transceiver architecture for single or dual antenna use, utilizing internal, external, or no diplexer, and allowing internal or external oscillator references.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
These objects are accomplished with the present invention by a RF front end to an IF generator and post-processor whereby the IF generator output is variable. The transceiver up-conversion path includes an IF Filter, the output of which is input to a mixer with the output of a fixed Phase Locked Oscillator (PLO). The mixer output is input to a band-pass filter and amplified. With a single antenna configuration, the amplifier output connects to either an internal or external diplexer that interfaces to the antenna. With a dual antenna configuration, the amplifier output interfaces directly to the transmit antenna. Similarly, the down-conversion path includes an internal or external diplexer in the single antenna configuration, a band-pass filter, a RF amplifier, a mixer that receives the RF amplifier output and the fixed PLO as inputs, an IF Filter, IF amplifier, and an attenuator for interfacing to the IF post-processor. A user-interface allows RF TX and RX frequency selection, data rate selection, and configurable options including internal or external diplexer, internal or external oscillator reference, and TX amplifier keying to allow simplex, half duplex, or full duplex communication.